Re: [ntpwg] [dhcwg] Re: Network Time Protocol (NTP) Options for DHCPv6

[Danny Mayer <[e-mail]>]

Mark Stapp wrote:
> making it possible to convey NTP servers in dhcpv6 doesn't seem to me to 
> be any different than conveying them in dhcpv4 was. that was done 
> something like ten years ago, and as far as I know that hasn't been a 
> problem.
> 
> I do wonder why some folks seem to think that using DNS names would 
> somehow be "safer" than using v6 addresses. if someone shipped a server 
> with a canned list of DNS names for NTP servers, there would be a 
> problem until the owners of the NTP servers named moved them. I don't 
> see how that'd be any better than the analogous mistake involving IP 
> addresses.
> 

Mark,

Slipping on my DNS hat for a moment, the whole point of DNS is that you
don't have to hardcode IP addresses in everything. You also benefit by
being able to put more than one IP address for the same name. It's safer
because the admin of the server doesn't have to worry when he moves a
service from on server to another. All he/she has to do is update the
DNS and not notify 1 million or so people that it's been moved. Can you
imagine moving a web server without it?

> shipping a DHCP server with a canned configuration would not be good, so 
> let's hope it doesn't happen. Mark Andrews's email seems to me to 
> summarize what happens: 'home' routers have a dhcp client face and a 
> dhcp server face, and use the client to populate the server.
> 
> aside from the catastrophe hypothetical, is there any really strong 
> reason - anything to do with the NTP protocol - that would prevent the 
> use of ipv6 addresses?
> 

It does use IPv6 addresses when it's presented with one. Now what
happens if that address is not running an NTP server? With DNS you can
get more than one address back and try another address or requery the
DNS to see if the address changed.

Danny

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